1. Technical Field
The present disclosure relates to an apparatus for surgically treating tissue. In particular, the disclosure relates to a mechanism for maintaining a drive cable in a relaxed configuration and imparting a tensile force to the drive cable prior to use of the apparatus.
2. Background of Related Art
Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaws that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaws may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaws. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis, which may facilitate the transection of the sealed tissue. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al.
Some endoscopic forceps are provided with a distal articulating portion to permit orientation of the jaws relative to a surgical site within the body of a patient. Mechanisms for articulating the distal end of an endoscopic instrument typically include a pair of drive cables or tensile members with distal ends anchored to the articulating portion on opposite sides of an instrument axis. The proximal ends of the drive cables are operatively coupled to an actuator that is responsive to an operator to draw one of the drive cables proximally while simultaneously permitting distal motion in the other drive cable. This motion in the drive cables induces pivotal motion of the distal end of the instrument.
The responsiveness of an articulating mechanism tends to be enhanced when the drive cables are configured to bear a tensile force. An adequate tensile force in the drive cables provides rigidity at the distal end of the instrument that permits a surgeon to perform procedures such as retraction and tissue tensioning. A drive cable under a tensile stress for a prolonged period is subject to creep deformation. Over extended periods of time, five years during storage of the instrument for example, a reduction of the tension in the drive cables may occur due to creep deformation. Accordingly, it may be beneficial to provide an apparatus to permit a surgical instrument to be stored with drive cables in an unstressed state, and to permit an operator to impart a tensile force to the drive cables prior to using the instrument.